1. Field
Aspects of the present invention generally relate to a method and apparatus for measuring a semiconductor substrate temperature. More specifically, aspects of the present invention relate to a method and apparatus for measuring a semiconductor substrate temperature by substrate infrared transmission.
2. Description of the Related Art
Ultra-large-scale integrated (ULSI) circuits may include more than one million electronic devices (e.g., transistors) that are formed on a semiconductor substrate, such as a silicon (Si) substrate, and cooperate to perform various functions within the device. During processing, a number of thermal processing steps are occasionally performed on the substrate surface. Thermal processing typically requires precise substrate temperature measurement for process control. Inaccurate substrate temperature control may result in poor process results that may adversely influence device performance and/or result in substrate film material damage.
Different types of temperature measurement tools may be used to measure substrate temperature during thermal processing. For example, thermocouples are often used to measure a substrate temperature by physically contacting the substrate at predetermined locations on the substrate surface. However, with larger diameter substrates, the overall temperature variation across substrate surface is difficult to determine due to the large distances between measurement locations. Furthermore, the reliability of the thermal physical contact of the thermocouples to the substrate surface is hard to control and has contamination concerns.
Alternatively, optical pyrometry is sometimes used to measure substrate temperature. Radiation emitted from the substrate surface during thermal processing is measured by an optical pyrometry sensor to determine the substrate temperature. However, the measurement of optical emissions from substrate surface is difficult to separate from background noise, such as intense lighting from heating lamps, optical emissions from chamber wall and/or stray light from windows. As the optical emissions from the substrate surface may not be accurately measured and the background noise may further introduce error to temperature measurement, the actual substrate surface temperature is difficult to precisely measure, which may result in erroneous substrate temperature determination and consequently poor processing results.
Therefore, there is a need for an improved method and apparatus for substrate temperature measurement during thermal processing.